Electron microscopic examination of wastewater biofilm formation and structural components

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Abstract
This research documents in situ wastewater biofilm formation, structure and physicochemical properties as revealed by scanning and transmission EM. Cationized ferritin was used to label anionic sites of the biofilm glycocalyx for viewing in thin section. Wastewater biofilm formation paralleled the processes involved in marine biofilm formation. Scanning EM revealed a dramatic increase in cell colonization and growth over a 144 h period. Constituents included a variety of actively dividing morphological types. Many of the colonizing bacteria were flagellated. Filaments were seen after primary colonization of the surface. Transmission EM revealed a dominant gram-negative cell wall structure in the biofilm constituents. At least 3 types of glycocalyces were observed. The predominant glycocalyx possessed interstices and was densely labeled with cationized ferritin. Two of the glycocalyces appeared to mediate biofilm adhesions to the substratum. Thus, the predominant glycocalyx of this thin wastewater biofilm evidently serves, in part, to enclose the bacteria in a matrix and anchor the biofilm to the substratum and to provide an extensive surface area with polyanionic properties.